At low tide, take a walk from the south end of Piha beach to The Gap and you go past the Green Rock. You walk along a rocky shelf and when you descend to the sand, this is at the Green Rock. It is a huge hollow cave, half a sphere in shape, clearly some catastrophic volcanic event has occured here to blast out this huge indentation.

Algae on the Green Rock

Water from a small stream drips down from above and this has caused the growth of a green algae over the rock, hence the name. It really is bright green in colour. Up above the green area, there is a ledge with a spike sticking out of the cliff. This is reputedly where a chain was tethered across the bay in the 1870s, in an attempt to create a raft of logs to float out to sea. How to get the kauri logs out of Piha exercised a number of minds for about 40 years till theÂ hauler was built from Karekare to Piha.

The raft idea was a failure as the logs got smashed as they tried to pull them out of the bay.